Methods and systems for displays with chromatic correction with differing chromatic ranges

ABSTRACT

There are provided a method and system for color correcting displays with different color gamuts. The method includes performing color correction on source picture content, using at least one of a non-reference type display having a non-reference color gamut and a reference type display having a reference color gamut. The performing step includes mastering the source picture content to provide mastered color corrected picture content for display on the reference type displays having a reference color gamut. The performing step further includes generating metadata for a subsequent inverse color gamut mapping that color transforms the mastered color corrected picture content for display on non-reference type displays having a non-reference color gamut. The subsequent inverse color gamut mapping is an inverse operation of a color gamut mapping applied during the color correction to obtain the mastered color corrected picture content for display on the reference type displays having the reference color gamut. The source picture content is mastered only for the reference type displays having the reference color gamut.

This application claims the benefit, under 35 U.S.C. § 365 ofInternational Application PCT/FR2007/052525, filed Dec. 14, 2007, whichwas published in accordance with PCT Article 21(2) on Oct. 16, 2008 inFrench and which claims the benefit of U.S. provisional patentapplication No. 60/921,579, filed Apr. 3, 2007.

The present principles relate generally to television displays and, moreparticularly, to a method and system for color correcting to providepredictable results on displays with different color gamuts.

In today's motion picture industry, colors of motion picture content aremostly graded for displays with a single color gamut defined by cathoderay tube (CRT) phosphor colors, corresponding to either the EuropeanBroadcasting Union (EBU) or the Society of Motion Picture and TelevisionEngineers color standard (SMPTE-C) for Standard Definition, and theInternational Telecommunication Union (ITU) 709 colors for HighDefinition. These are the current standards for use in determining thereference color gamut (RCG) for displays. However, displays withnon-standard color gamuts are currently prevalent among consumers ofmotion picture content.

When editing the colors of a picture on a display with a reference colorgamut other than the color gamut of the target display, the resultantcolors may look dissatisfying on the target display. To illustrate caseswhere the resultant colors may look dissatisfying, the following twocases are described.

The first case relates to consumer displays having color gamuts roughlythe same size as the reference display, but the display primaries arenot equal to the display primaries of the reference display duringcontent creation. In such circumstances, it is desirable to ensure thatthe colors can be accurately represented on the consumer displays.

The second case relates to the current existence of wide gamut colordisplays being utilized in the field. In such circumstances, no methodsexist to color correct consumer displays with respect to these widegamut color displays. For example, such consumer displays may use adifferent reference color gamut but may or may not be capable of evendisplaying colors in accordance with the wide gamut color standards.

There is an analogy to the situation when color television was initiallyintroduced in the United States. A lot of different sets of primarieswere being utilized at that time that would not allow for a unifiedcolorimetric. However, the stockpiling by one of the primary televisionmanufacturers of a significant amount of phosphors produced by aparticular phosphor manufacturer resulted in the effective formation ofa quasi standard and, then, ultimately a standard (SMPTE-C). However,the Federal Communications Commission (FCC) never adopted this and thetelevision manufacturing industry had to live with this dichotomy. Therewere attempts by the Society of Motion Picture and Television Engineers(SMPTE) to emulate National Television System Committee (NTSC) colors ona SMPTE-C monitor which eventually failed due to technology reasons atthat time.

The color gamut of a display is determined by the display technologychosen. At this moment, a consumer has the choice between the followingtechnologies (also referred to herein as “display type”) including, forexample, liquid crystal display (LCD), Plasma, cathode ray tube (CRT),digital light processing (DLP), and silicon crystal reflective display(SXRD). However, there can be significant differences between differentdisplay technologies, as well as between two representatives of the samedisplay technology. For example, two liquid crystal display sets can beequipped with different sets of light sources. One of these sets oflight sources may be cold cathode fluorescent lights (CCFL), where thecolor gamut mainly depends on the phosphors used. Historically, theselight sources did not permit the use of a high color gamut. In fact,displays that used these light sources could not reproduce all 709colors, as per the International Telecommunication Union (ITU) 709 colorstandard for high definition. However, recent developments have broughtproducts to market that use so-called wide gamut cold cathodefluorescent lights (W-CCFL), where the color gamut is even larger thanthe 709 color gamut. Another component of liquid crystal displaytechnology is the color filters, which could be designed to have a highlight output and, thus, a high light efficiency with a narrow colorgamut, or could be designed to have a luminous light efficiency and awider color gamut. Another trend is that LCD display's CCFL back lightunits (BLU's) get replaced by RGB LED (Light Emitting Diodes) BLU's withan even higher color gamut.

Digital light processing displays and silicon crystal reflectivedisplays (including rear projection) displays are reflective displaysthat filter light coming from a light source. Currently, there aredifferent techniques to increase the color gamut of those devices. Infact, as of today, some of the displays employing these differenttechniques already have an increased color gamut compared to the currentapplicable reference color gamut.

With the advent of wide gamut displays, it has become possible todisplay a wider range of colors than was previously possible. Thecurrent video content on digital video disks (DVD's), televisionbroadcasts, and/or via video over Internet Protocol (VoIP), are encodedin a color space with a reference color gamut and, thus, follow therules that were set many years ago when wide gamut color display was notfeasible. In fact, until recently it was difficult to achieve areproduction even of the current reference color gamut.

As it looks today, the situation has changed. An extended color gamut isfeasible and there is a desire to utilize the wider color gamut.However, instead of choosing another set of wide color gamut primaries,the current trend that seems to be preferred is the use of open,unrestrictive color standards. One example of such standard is XYZ forDigital Cinema, or xvYCC (IEC 61966-2-3) for consumer television. Otherexamples include, for example, sYCC (International ElectrotechnicalCommission (IEC) 61966-2-1), ITU-R BT.1361, or e-sRGB (Photographic andImaging Manufacturers Association (PIMA) 7667) for computer graphics andstill picture photography.

At the same time, there is significant variation in the color gamutsused in various displays currently available. Until recently, the colorgamut was determined more or less by the standard cathode ray tubephosphors. Today, the range of colors capable of being displayed dependson the display technology used and the hardware design, as describedabove. Turning to FIG. 1, color gamut measurements of currentlyavailable displays are indicated generally by the reference numeral 100.As is evident, there currently exists a significant amount ofdifferences between the current available color gamut measurements 100.It is to be noted that none of the color gamuts of the various availabledisplays are equal to the reference color gamy of the source materialwhich, in this example, corresponds to ITU-R Bt. 709. With respect toFIG. 1, the display with the widest color gamut was a liquid crystal onsilicon (LCOS) display under test, with a yellowish Green, and a liquidcrystal display (LCD) with a wide gamut backlight with a cyanic Green.

Additionally, current displays seem to simply replace the referencecolor primaries specified by the applicable standard by the colorprimaries corresponding to the respective display (e.g., respectivedisplay type, respective color gamut implemented on that display, and soforth), similar to the past and the use of different cathode ray tubephosphors. As a consequence, colors do not appear as they should. Thatis, colors appear different than what they were intended to appear like.For instance, fir trees look like pine trees, tomatoes look likeoranges, and so forth. However, mapping primaries is the most primitiveand cheapest way of gamut mapping.

In the case of wide gamut material on a wide gamut display, there stillis a problem where colors may be displayed incorrectly due to the colorgamut of the wide gamut material being different than the color gamut ofthe wide gamut display. In fact, by using the above mentionedunrestrictive color standards like xvYCC or XYZ, it is always possiblethat a color gets transmitted that cannot be displayed on one or moreparticular wide gamut displays.

One method for color correction involves 3×3 matrixing the sourceprimaries to the display primaries (which, however, requires a priorvideo signal linearization). This solution has problems when colors aretransmitted that are beyond the color gamut of the display color gamut.As an example, consider a display with three primaries of Red, Green,and Blue, where the color to be displayed may be a Green color (e.g., avariation of the primary color Green), and that color may be out of thedisplay range. The typical result of such a situation is that the colorto be displayed may get clipped to their respective maximum ranges. Theproblem will manifest in a wrong color reproduction, in a hue,saturation, and also brightness error. The detrimental affect will beeven worse if the color appears in a gradation (e.g., as seen most oftenin animated movies), as a false contour will also appear. A falsecontour is the appearance of an erroneous structure or object in thepicture as a result of artifacts in the video signal processing or inthe display.

Consider another example, as follows. A “cyanish” white color is definedas follows: Blue=Max; Red=0.8*Max; and Green=Max; on a wide gamutdisplay, where “max” represents the maximum permissible value. On anarrow gamut display that has less saturated Blue, this will result in aclipping of Blue, and the White will become Greenish. This problem isillustrated in FIG. 3. Turning to FIG. 3, a hue change on a bluish whitegraduation due to color gamut restriction is indicated generally by thereference numeral 300. In particular, the desired result is shown on theleft portion of FIG. 3 and is designated by the reference numeral 310,while the actual result is shown on the right portion of FIG. 3 and isdesignated by the reference numeral 350. As indicated by the referencenumeral 380 and the corresponding text, White turns Yellow due toclipping in Blue.

It is therefore essential that a proper way of color gamut mapping isused for rendering colors on the display used. Turning to FIG. 2, anexample color gamut mapping is indicated generally by the referencenumeral 200. FIG. 2 shows a “Color Gamut 1” and a “Color Gamut 2” as across section, where “Color Gamut 1” is mapped into “Color Gamut 2” bymeans of color gamut mapping. In the color gamut mapping 100, variationin luminance is shown with respect to the vertical axis (typicallydenoted as the Y axis), and variance in chrominance is shown withrespect to the horizontal axis (typically denoted as the X axis). Theprovided example is for a “Color Gamut 2” smaller than “Color Gamut 1”.However, it is to be appreciated that the opposite case is alsopossible, where “Color Gamut 2” is larger than “Color Gamut 1”.

Turning to FIG. 4, an exemplary high-level diagram showing the workflowfor color correction using a display having a reference color gamut forcontent that may be subsequently displayed on a display with a differentcolor gamut than the reference color gamut is indicated generally by thereference numeral 400.

The undesirable result of the color correction workflow 400 of FIG. 4 isthat when color correcting on a display with a reference color display(RCG), the colors on a display with a second color gamut or color gamut2(CG2) will be reproduced incorrectly.

The color correction workflow 400 involves a content creation side 480and a content consumer side 490. A RCG display 482 is used on thecontent creation side 480. A RCG display 492 and a CG2 display 494 areused on the content consumer side 590.

The picture source content may be stored, for example, in a picturesource content store 420. The color corrected picture content may bestored, for example, in a color corrected picture content store 440.

A color correction module 430 generates the content that only lookscorrect on a display of the same type and with the same color gamut.Thus, the colors on the CG2 display will not look the same as the colorsthat were color corrected on the RCG display. It is very likely that atleast some of the colors on the RCG2 display will be clipped and atleast some with be displayed with the wrong hue.

The problem is illustrated in FIG. 4 using the “Ski Image”, which ispart of the CIE TC8-03 test images in their “Guidelines for theEvaluation of Gamut Mapping Algorithms”. It is courtesy of FujifilmElectronic Imaging Ltd. (UK). As we can see, on the content consumerside, the picture can only be retrieved correctly on a display with RCG.The picture will look incorrect and it will show the above mentionedartifacts if a display with a color gamut not equal to the RCG (CG2) isused for display.

These and other drawbacks and disadvantages of the prior art areaddressed by the present principles, which are directed to a method andsystem for color correcting to provide predictable results on displayswith different color gamuts.

According to an aspect of the present principles, there is provided amethod for color correcting. The method includes performing colorcorrection on source picture content, using at least one of anon-reference type display having a non-reference color gamut and areference type display having a reference color gamut. The performingstep includes mastering the source picture content to provide masteredcolor corrected picture content for display on the reference typedisplays having a reference color gamut. The performing step furtherincludes generating metadata for a subsequent inverse color gamutmapping that color transforms the mastered color corrected picturecontent for display on non-reference type displays having anon-reference color gamut. The subsequent inverse color gamut mapping isan inverse operation of a color gamut mapping applied during the colorcorrection to obtain the mastered color corrected picture content fordisplay on the reference type displays having the reference color gamut.The source picture content is mastered only for the reference typedisplays having the reference color gamut.

According to another aspect of the present principles, there is provideda system for color correcting. The system includes a color correctionmodule for performing color correction on source picture content, usingat least one of a non-reference type display having a non-referencecolor gamut and a reference type display having a reference color gamut,to provide mastered color corrected picture content for display on thereference type displays having a reference color gamut. The systemfurther includes a color gamut mapping module for performing a colorgamut mapping with respect to the mastered color corrected picturecontent for display on the reference type displays having the referencecolor gamut to generate metadata for a subsequent inverse color gamutmapping with respect to the color gamut mapping. The subsequent inversecolor gamut mapping color transforms the mastered color correctedpicture content for display on non-reference type displays having anon-reference color gamut. The source picture content is mastered onlyfor the reference type displays having the reference color gamut.

These and other aspects, features and advantages of the presentprinciples will become apparent from the following detailed descriptionof exemplary embodiments, which is to be read in connection with theaccompanying drawings.

The present principles may be better understood in accordance with thefollowing exemplary figures, in which:

FIG. 1 is a diagram showing color gamut measurements of currentlyavailable displays, in accordance with the prior art;

FIG. 2 is a diagram showing an example color gamut mapping, inaccordance with the prior art;

FIG. 3 is a diagram showing a hue change on a bluish white graduationdue to color gamut restriction, in accordance with the prior art;

FIG. 4 is a high-level diagram showing the exemplary workflow for colorcorrection using a display having a reference color gamut for contentthat may be subsequently displayed on a display with a different colorgamut than the reference color gamut, in accordance with the prior art;

FIG. 5 is a high-level diagram showing the exemplary workflow for colorcorrection to obtain a master for RCG displays and metadata for CG2displays, in accordance with an embodiment of the present principles;

FIG. 6 is a high-level diagram showing the exemplary workflow for colorcorrection to obtain a master for CG2 displays and one master for RCGdisplays, in accordance with an embodiment of the present principles;

FIG. 7 is a high-level diagram showing another exemplary workflow forcolor correction to obtain a master for RCG displays and metadata forCG2 displays, in accordance with an embodiment of the presentprinciples; and

FIG. 8 is a high-level diagram showing another exemplary workflow forcolor correction to obtain a master for CG2 displays and one master forRCG displays, in accordance with an embodiment of the presentprinciples.

The present principles are directed to a method and system for colorcorrecting to provide predictable results on displays with differentcolor gamuts.

The present description illustrates the present principles. It will thusbe appreciated that those skilled in the art will be able to devisevarious arrangements that, although not explicitly described or shownherein, embody the present principles and are included within its spiritand scope.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the presentprinciples and the concepts contributed by the inventor(s) to furtheringthe art, and are to be construed as being without limitation to suchspecifically recited examples and conditions.

Moreover, all statements herein reciting principles, aspects, andembodiments of the present principles, as well as specific examplesthereof, are intended to encompass both structural and functionalequivalents thereof. Additionally, it is intended that such equivalentsinclude both currently known equivalents as well as equivalentsdeveloped in the future, i.e., any elements developed that perform thesame function, regardless of structure.

Thus, for example, it will be appreciated by those skilled in the artthat the block diagrams presented herein represent conceptual views ofillustrative circuitry embodying the present principles. Similarly, itwill be appreciated that any flow charts, flow diagrams, statetransition diagrams, pseudocode, and the like represent variousprocesses which may be substantially represented in computer readablemedia and so executed by a computer or processor, whether or not suchcomputer or processor is explicitly shown.

The functions of the various elements shown in the figures may beprovided through the use of dedicated hardware as well as hardwarecapable of executing software in association with appropriate software.When provided by a processor, the functions may be provided by a singlededicated processor, by a single shared processor, or by a plurality ofindividual processors, some of which may be shared. Moreover, explicituse of the term “processor” or “controller” should not be construed torefer exclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (“DSP”)hardware, read-only memory (“ROM”) for storing software, random accessmemory (“RAM”), and non-volatile storage.

Other hardware, conventional and/or custom, may also be included.Similarly, any switches shown in the figures are conceptual only. Theirfunction may be carried out through the operation of program logic,through dedicated logic, through the interaction of program control anddedicated logic, or even manually, the particular technique beingselectable by the implementer as more specifically understood from thecontext.

In the claims hereof, any element expressed as a means for performing aspecified function is intended to encompass any way of performing thatfunction including, for example, a) a combination of circuit elementsthat performs that function or b) software in any form, including,therefore, firmware, microcode or the like, combined with appropriatecircuitry for executing that software to perform the function. Thepresent principles as defined by such claims reside in the fact that thefunctionalities provided by the various recited means are combined andbrought together in the manner which the claims call for. It is thusregarded that any means that can provide those functionalities areequivalent to those shown herein.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles means that a particular feature, structure,characteristic, and so forth described in connection with the embodimentis included in at least one embodiment of the present principles. Thus,the appearances of the phrase “in one embodiment” or “in an embodiment”appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

As used herein, the acronym “CG” denotes “color gamut”, the acronym“CGM” denotes “color gamut mapping”, the acronym “RCG” denotes“reference color gamut”, and the acronym “CG2” denotes “color gamut 2”.

Also, as used herein, the phrase “RCG displays” refers to displayshaving a gamut type denoted as a reference color gamut (RCG), while thephrase “CG2 displays” refers to displays having a gamut type denoted asa second color gamut, the second color gamut being different than thereference color gamut.

It is to be appreciated that while the disclosure provided herein issubstantially described with respect to, for example, a picture versionfor RCG displays, and a picture version for CG2 displays, or metadatafor reconstructing the picture for CG2 displays, given the variety ofavailable consumer displays, more than one CG2 version may be generated,while maintaining the spirit of the present principles.

Moreover, as used herein, the phrase “709 color gamut” and variationsthereof denote 709 colors which, in turn, denote, the color cube definedby the three phosphor primaries and the white point defined in ITU-RBt.709.

Also, as used herein, with respect to the transmission and receipt ofmetadata, the phrase “in-band” refers to the transmitting and/orreceiving of such metadata together with the color corrected picturecontent to be displayed by a consumer device. In contrast, the phrase“out-of-band” refers to the transmitting and/or receiving of themetadata separately with respect to the color corrected picture contentto be displayed by a consumer device.

Further, as used herein, the phrases “color correction” and “colorgrading” interchangeably refer to the creative process during postproduction to tune colors so that the picture expresses the creativeintent.

Additionally, as used herein, the phrase “master” refers to mastereddisplay content, where the display content is mastered for a particularcolor gamut such as, for example, RCG or CG2.

Also, as used herein, the term “metadata” refers to data such as, forexample, integer, non-integer values, and/or Boolean values, used tocontrol, turn on or turn off color processing mechanisms, and to modifythe functionality of such. Furthermore, metadata may include aspecification of a mapping table.

For example, in an embodiment, a color mapping table could be realizedby means of a 3-D LUT (three-dimensional Look Up Table). This LUT isused to receive three input values, each value representing one colorcomponent, Red, Green, or Blue, and producing a predefined triplet ofoutput values, e.g., Red, Green, and Blue, for each individual Red,Green, and Blue input triplet. In this case, the metadata from contentcreation to consumer would then include a LUT specification.

Another embodiment may involve the specification of a mapping functionsuch as, for example, circuitry and/or so forth for performing a “GOG”(Gain, Offset, Gamma), which is defined as follows:Vout=Gain*(Offset+Vin)^Gamma, for each color component.

In this case, the metadata would include 9 values, one set of Gain,Offset, and Gamma for each of the three color components.

Of course, the present principles are not limited to the precedingembodiments and, given the teachings of the present principles providedherein, other embodiments involving other implementations of metadataare readily contemplated by one of ordinary skill in this and relatedarts, while maintaining the spirit of the present principles.

Moreover, as used herein, the phrase “color correction” refers to acreative procedure to manually choose the right (preferred) colors onthe content creation side (versus the consumer consumption side).Accordingly, the phrase “color correction module” and similar phrasesrefer to the structure required for a colorist to manually correct suchcolors. Thus, such structure may involve an interface presented to thecolorist such as a graphical user interface (GUI), selection means forallowing the colorist to make selections regarding, for example, colorsto be replaced and/or modified, and implementing means for implementingthe selections made by the colorist. The selection means may include oneor more of the following: a keyboard; a keypad; a mouse; buttons;switches; and so forth.

As noted above, the present principles are directed to a method andsystem for color correcting to provide predictable results on displayswith different color gamuts. The present principles correct differencesin colors between different target displays. It is to be appreciatedthat the present principles are directed to current content (e.g.,encoding types and technologies) and displays (e.g., display types, anddifferences between the same, as well as different display types,resulting from, for example, hardware, software, and so forth) as wellas future content and displays, as they relate to the use of differentcolor gamuts.

In an embodiment, the present principles may be used to address anexemplary problem where color correction is to be performed on a displaywith a reference color gamut, however, the corrected colors are to bedisplayed on a display with a different color gamut than the referencecolor gamut used for color correction.

Turning to FIG. 5, a high-level diagram showing the exemplary workflowfor color correction to obtain a master for RCG displays and metadatafor CG2 displays is indicated generally by the reference numeral 500.

The color correction workflow 500 involves a content creation side 580and a content consumer side 590. The color correction 530 is done basedon a color gamut for CG2 displays. A CG2 display 584 shall be directlyattached to the color correction tool. A CGM 586 is used to map thecontent from a color gamut for display on CG2 display 584 to a colorgamut for display on RCG display 582, and the resultant picture contentis then used for distribution/storage in color corrected picture contentstore 540. An RCG display 592 and a CG2 display 594 are used on thecontent consumer side 590.

In the embodiment, the use of the present principles provides acontrolled color difference between the content displayed on the RCGdisplay 592 and the CG2 display 594 on the content consumer side 590 asthe distinctive feature. As noted above, the embodiment involves the useof a master, i.e., one version of mastered content, for (use by) RCGdisplays and metadata for (use by) CG2 displays.

The metadata 510 describes a transformation of picture source contentinto color corrected picture content. The picture source content ismastered for RCG displays but is color corrected for CG2 displays (thususing the CG2 to RCG GMM described above) and the color correctedpicture content relates to colors for RCG displays. Thus, the metadatamay describe, for example, the difference between the colors for a CG2display and a RCG display. That is, the metadata may describe, forexample, an inverse transform of the CGM 586 used for color correction,or, the metadata may describe the CGM 586 itself and the CGM block 596has the processing capacity to invert the CGM description.

The picture source content may be stored, for example, in a picturesource content store 520. The color corrected picture content may bestored, for example, in a color corrected picture content store 540. Themetadata 510 may be stored, for example, in a metadata store 517.

A color correction module 530 generates the RCG master and the metadatafor CG2 displays.

On the content creation side 580, the RCG mastered content, colorcorrected for CG2, is provided to the CGM module 586 that performs a CG2to RCG GMM so that the RCG mastered content is color corrected fordisplay on the RCG display 582.

On the content consumer side 590, the RCG mastered content, colorcorrected for CG2, is provided directly to the RCG display 592 withoutthe use or need of the metadata or a color gamut mapping.

Moreover, on the content consumer side 590, the RCG mastered content,and the metadata for the CG2 displays is applied to a CGM module 596that performs an inverse color gamut mapping (i.e., RCG to CG2 GMM) sothat the RCG mastered content is transformed for display on the CG2display 594. That is, by transmitting the inverse of the CG2 to RCG CGM(which will be a RCG to CG2 CGM) to the CG2 display 594, the CG2 display594 is able to do the inverse of the CG2 to RCG CGM operation andretrieve the CG2 device colors.

Turning to FIG. 6, a high-level diagram showing the exemplary workflowfor color correction to obtain a master for CG2 displays and one masterfor RCG displays is indicated generally by the reference numeral 600.

The color correction workflow 600 involves a content creation side 680and a content consumer side 690. A RCG display 682 is used on thecontent creation side 680. In addition, a CG2 display 684 shall be usedon the content creation side 580 for proof viewing the content meant forconsumer RCG displays. A RCG display 692 and a CG2 display 694 are usedon the content consumer side 690.

In an embodiment, the color correction will result in a master for CG2displays (such as CG2 display 694), and a master for RCG displays (suchas RCG display 692). In an embodiment, the master for the RCG displayswould be a derivative of the master for CG2 displays. The approach ofFIG. 6 provides a controlled color difference between a consumer CG2display and a RCG display 590 as the distinctive feature. The quality ofthe color accuracy is subject to the CG2 specifications used for colorcorrection matching those used in the field, or the display in the fieldbeing calibrated to the specification used for color correction.

The picture source content may be stored, for example, in a picturesource content store 620. The color corrected picture content for RCGdisplays, i.e., the master for RCG displays, may be stored, for example,in a color corrected picture content store 645. The color correctedpicture content for CG2 displays, i.e., the master for CG2 displays, maybe stored, for example, in a color corrected picture content store 640.

On the content creation side, a color correction module 630 generatesthe CG2 master. Moreover, on the content creation side 680, the CG2mastered content is applied to a CGM module 686 that performs a colorgamut mapping to generate the RCG master, so that the CG2 masteredcontent is color corrected for display on the RCG display 682.

On the content consumer side 690, the RCG mastered content is provideddirectly to the RCG display 692 without the need for a color gamutmapping, and the CG2 mastered content is provided directly to the CG2display 694 without the need for a color gamut mapping.

There is a singular specification for the RCG display, and yet multiplespecifications will have to be considered for CG2 displays so, in anembodiment, it would be advantageous if the “mother” version was theversion for RCG displays. In some circumstances, the color correctionprocess may be a bit cumbersome since the colors are being modified witha non-linear mapping between the color correction and the referencedisplay. Some colors may not change as initially expected by thecolorist. However, there will be no colors in the master that cannot bedisplayed by a display with CG2, nor will there be a color that cannotbe displayed by a RCG display. This is a real benefit of this approach.

Turning to FIG. 7, a high-level diagram showing the exemplary workflowfor color correction to obtain a master for RCG displays and metadatafor CG2 displays is indicated generally by the reference numeral 700.

The color correction workflow 700 involves a content creation side 780and a content consumer side 790. A RCG display 782, using CG2 simulationvia a CGM module 786, is used on the content creation side 780.Alternatively or in addition, a CG2 display may be used on the contentcreation side 780. A RCG display 792 and a CG2 display 794 are used onthe content consumer side 790.

In the embodiment, the use of the present principles provides acontrolled color difference between the content displayed on the RCGdisplay 792 and the CG2 display 794 on the content consumer side 790. Asnoted above, the embodiment involves the use of a master, i.e., oneversion of mastered content, for (use by) RCG displays (when renderedusing a CGM that simulates a CG2 display on a RCG display, i.e., a CG2to RCG GMM is used) and metadata for (use by) CG2 displays.

The metadata 710 describes a transformation of picture source contentinto color corrected picture content. The picture source content ismastered for RCG displays but is color corrected for CG2 displays (thususing the CG2 to RCG GMM described above for rendering of the RCGmastered content on RCG displays) and the color corrected picturecontent relates to colors for RCG displays. Thus, the metadata maydescribe, for example, the difference between the colors for a CG2display and a RCG display. That is, the metadata may describe, forexample, an inverse transform of the CG2 simulation used for colorcorrection,

The picture source content may be stored, for example, in a picturesource content store 720. The color corrected picture content may bestored, for example, in a color corrected picture content store 740. Themetadata 710 may be stored, for example, in a metadata store 717.

A color correction module 730 generates the RCG master and the metadatafor CG2 displays.

On the content creation side 780, the RCG mastered content, colorcorrected for CG2, is provided to the CGM module 786 that performs a CG2to RCG GMM so that the RCG mastered content is color corrected fordisplay on the RCG display 782.

On the content consumer side 790, the RCG mastered content, colorcorrected for CG2, is provided directly to the RCG display 792 withoutthe use or need of the metadata or a color gamut mapping.

Moreover, on the content consumer side 790, the RCG mastered content,color corrected for CG2, and the metadata for the CG2 displays isapplied to a CGM module 796 that performs an inverse color gamut mapping(i.e., RCG to CG2 GMM) so that the RCG mastered content is colorcorrected for display on the CG2 display 794. That is, by transmittingthe inverse of the CG2 to RCG CGM (which will be a RCG to CG2 CGM) tothe CG2 display 794, the CG2 display 794 is able to do the inverse ofthe CG2 to RCG CGM operation and retrieve the CG2 device colors.

Turning to FIG. 8, a high-level diagram showing the exemplary workflowfor color correction to obtain a master for CG2 displays and one masterfor RCG displays is indicated generally by the reference numeral 800.

The color correction workflow 800 involves a content creation side 880and a content consumer side 890. A RCG display 882 is used on thecontent creation side 880. A RCG display 892 and a CG2 display 894 areused on the content consumer side 890.

In an embodiment, the color correction will result in a master for CG2displays (such as CG2 display 894), and a master for RCG displays (suchas RCG display 892). In an embodiment, the master for the RCG displayswould be a derivative of the master for CG2 displays. The approach ofFIG. 8 provides a match between a consumer CG2 display and a RCGdisplay. The quality of the match is subject to the CG2 specificationsused for color correction matching those used in the field, or thedisplay in the field being calibrated to the specification used forcolor correction.

The picture source content may be stored, for example, in a picturesource content store 820. The color corrected picture content for RCGdisplays, i.e., the master for RCG displays, may be stored, for example,in a color corrected picture content store 845. The color correctedpicture content for CG2 displays, i.e., the master for CG2 displays, maybe stored, for example, in a color corrected picture content store 840.

On the content creation side, a color correction module 830 generatesthe CG2 master. Moreover, on the content creation side 880, the CG2mastered content is applied to a CGM module 886 that performs a colorgamut mapping to generate the RCG master, so that the CG2 masteredcontent is color corrected for display on the RCG display 882.

On the content consumer side 890, the RCG mastered content is provideddirectly to the RCG display 892 without the need for a color gamutmapping, and the CG2 mastered content is provided directly to the CG2display 894 without the need for a color gamut mapping.

There is a singular specification for the RCG display, and yet multiplespecifications will have to be considered for CG2 displays so, in anembodiment, it would be advantageous if the “mother” version was theversion for RCG displays. In some circumstances, the color correctionprocess may be a bit cumbersome since the colors are being modified witha non-linear mapping between the color correction and the referencedisplay. Some colors may not change as initially expected by thecolorist. However, there will be no colors in the master that cannot bedisplayed by a display with CG2, nor will there be a color that cannotbe displayed by a RCG display. This is a real benefit of this approach.

On the content consumer side, circuitry will be provided that connectsthe signal source with a CG2 display. This circuitry can be implementedin hardware and/or in software, and provides the signal transform togenerate the CG2 version needed out of the picture for RCG displays

These and other features and advantages of the present principles may bereadily ascertained by one of ordinary skill in the pertinent art basedon the teachings herein. It is to be understood that the teachings ofthe present principles may be implemented in various forms of hardware,software, firmware, special purpose processors, or combinations thereof.

Most preferably, the teachings of the present principles are implementedas a combination of hardware and software. Moreover, the software may beimplemented as an application program tangibly embodied on a programstorage unit. The application program may be uploaded to, and executedby, a machine comprising any suitable architecture. Preferably, themachine is implemented on a computer platform having hardware such asone or more central processing units (“CPU”), a random access memory(“RAM”), and input/output (“I/O”) interfaces. The computer platform mayalso include an operating system and microinstruction code. The variousprocesses and functions described herein may be either part of themicroinstruction code or part of the application program, or anycombination thereof, which may be executed by a CPU. In addition,various other peripheral units may be connected to the computer platformsuch as an additional data storage unit and a printing unit.

It is to be further understood that, because some of the constituentsystem components and methods depicted in the accompanying drawings arepreferably implemented in software, the actual connections between thesystem components or the process function blocks may differ dependingupon the manner in which the present principles are programmed. Giventhe teachings herein, one of ordinary skill in the pertinent art will beable to contemplate these and similar implementations or configurationsof the present principles.

Although the illustrative embodiments have been described herein withreference to the accompanying drawings, it is to be understood that thepresent principles is not limited to those precise embodiments, and thatvarious changes and modifications may be effected therein by one ofordinary skill in the pertinent art without departing from the scope orspirit of the present principles. All such changes and modifications areintended to be included within the scope of the present principles asset forth in the appended claims.

The invention claimed is:
 1. A method for color correcting, comprising:performing color correction on source picture content, using at leastone of a non-reference type display having a non-reference color gamutand a reference type display having a reference color gamut, whereinsaid performing step comprises: mastering the source picture content toprovide mastered color corrected picture content for display on thereference type displays having a reference color gamut; and generatingmetadata for a subsequent inverse color gamut mapping that colortransforms the mastered color corrected picture content for display onnon-reference type displays having a non-reference color gamut, whereinthe metadata describes difference between colors of the non-referencetype displays and the reference type displays; and wherein thesubsequent inverse color gamut mapping is an inverse operation of acolor gamut mapping applied during the color correction to obtain themastered color corrected picture content for display on the referencetype displays having the reference color gamut, and the source picturecontent is mastered only for the reference type displays having thereference color gamut.
 2. The method of claim 1, wherein said step ofmastering the source picture content comprises rendering the masteredcolor corrected picture content on the reference type display using acolor gamut mapping that converts the source picture content for thenon-reference type display to picture content for the reference typedisplay.
 3. The method of claim 1, further comprising transmitting aspecification of the inverse color gamut mapping to at least one of thenon-reference type displays for consumer consumption.
 4. The method ofclaim 1, wherein the metadata is provided to the non-reference typedisplays for final consumption at least one of in-band and out-of-bandwith respect to the mastered color corrected picture content.
 5. Themethod of claim 1, wherein the reference type displays and thenon-reference type displays are at least one of liquid crystal displays,plasma displays, cathode ray tube displays, digital light processingdisplays, organic light emitting diode displays, liquid crystal onsilicon displays, and direct drive image light amplifier displays.
 6. Asystem for color correcting, comprising: a color correction module forperforming color correction on source picture content, using at leastone of a non-reference type display having a non-reference color gamutand a reference type display having a reference color gamut, to providemastered color corrected picture content for display on the referencetype displays having a reference color gamut; and a color gamut mappingmodule for performing a color gamut mapping with respect to the masteredcolor corrected picture content for display on the reference typedisplays having the reference color gamut to generate metadata for asubsequent inverse color gamut mapping with respect to the color gamutmapping, the subsequent inverse color gamut mapping color transformingthe mastered color corrected picture content for display onnon-reference type displays having a non-reference color gamut, whereinthe metadata describes difference between colors of the non-referencetype displays and the reference type displays; and wherein the sourcepicture content is mastered only for the reference type displays havingthe reference color gamut.
 7. The system of claim 6, wherein themetadata is provided to the non-reference type displays for finalconsumption at least one of in-band and out-of-band with respect to themastered color corrected picture content.
 8. The system of claim 6,wherein the reference type displays and the non-reference type displaysare at least one of liquid crystal displays, plasma displays, cathoderay tube displays, digital light processing displays, organic lightemitting diode displays, liquid crystal on silicon displays, and directdrive image light amplifier displays.
 9. A system for color correcting,comprising: means for performing color correction on source picturecontent, using at least one of a non-reference type display having anon-reference color gamut and a reference type display having areference color gamut, wherein said means for performing colorcorrection comprises: means for mastering the source picture content toprovide mastered color corrected picture content for display on thereference type displays having a reference color gamut; and means forgenerating metadata for a subsequent inverse color gamut mapping thatcolor transforms the mastered color corrected picture content fordisplay on non-reference type displays having a non-reference colorgamut, wherein the metadata describes difference between colors of thenon-reference type displays and the reference type displays; wherein thesubsequent inverse color gamut mapping is an inverse operation of acolor gamut mapping applied during the color correction to obtain themastered color corrected picture content for display on the referencetype displays having the reference color gamut, and the source picturecontent is mastered only for the reference type displays having thereference color gamut.
 10. The system of claim 9, wherein said means formastering the source picture content comprises means for rendering themastered color corrected picture content on the reference type displayusing a color gamut mapping that converts the source picture content forthe non-reference type display to picture content for the reference typedisplay.
 11. The system of claim 9, further comprising means fortransmitting a specification of the inverse color gamut mapping to atleast one of the non-reference type displays for consumer consumption.12. The system of claim 9, wherein the metadata is provided to thenon-reference type displays for final consumption at least one ofin-band and out-of-band with respect to the mastered color correctedpicture content.
 13. The system of claim 9, wherein the reference typedisplays and the non-reference type displays are at least one of liquidcrystal displays, plasma displays, cathode ray tube displays, digitallight processing displays, organic light emitting diode displays, liquidcrystal on silicon displays, and direct drive image light amplifierdisplays.